Ji Xiaoli,Chen Fan,Liu Jian,Ma Qianqian,Qiao Ruochen,Xu Zhihao
This study details microwave-absorbing materials made of multi-walled carbon nanotubes (MWCNTs) and silicon nitride (Si 3 N 4 ). The synthesis of MWCNTs/Si 3 N 4 nanocomposites (NCs) involves combining alkyne-functionalized multi-walled carbon nanotube (MWCNTs-ALK) nanoparticles (NPs) with azide-functionalized silicon nitride (Si 3 N 4 –N 3 ) NPs through a click reaction. In order to analyze the morphology and structure of the MWCNTs/Si 3 N 4 NCs, scanning electron microscopy, x-ray photoelectron spectroscopy, x-ray diffraction, and infrared analysis techniques are employed. The electromagnetic properties of the NCs are evaluated using a vector network analyzer. The results indicate when this feeding ratio of MWCNTs-ALK and Si 3 N 4 –N 3 was 1:2 and a matching thickness of 3.0 mm at 6.82 GHz, the minimum reflection loss reaches − 30.7 dB. Additionally, with a feeding ratio of 1:1 and a matching thickness of 1.5 mm, the bandwidth below − 10 dB ranges from 11.6 to 15.8 GHz. The compositions of MWCNTs/Si 3 N 4 synthesized by click reactions indicate that, compared to physical mixed samples, our material has superior wave-absorbing properties. This improvement can be attributed to the covalent bonding between MWCNTs and Si 3 N 4 facilitated by the click reaction, resulting in enhanced dielectric loss and impedance matching. The results of this study have significant implications for the processing of composite microwave-absorbing materials and offer novel insights into the design of multifunctional microwave-absorbing materials. Graphical
While ultrafast charging and discharging is highly desired for energy storage, the densely packed crystalline inorganic electrodes suffer from sluggish ion transport that limits this capability. Here we report two-dimensional vertical ladder polymer cathode materials that feature layered nanosheets with rich intralayer pores and structural defects alongside weak interlayer interactions. This structural design allows lithium ions to migrate vertically across the intrinsic pores and/or defects accompanied by horizontal intercalation, thus establishing a cross-flow pathway for lithium storage. Such an effective ion-transport method enables flash charging of an ultrahigh-power polymer cathode to ~70% state-of-charge within 30 s at a high current density. Even operated at −50 °C, the polymer cathode achieves 3-min charging to ~55% state-of-charge. Furthermore, we propose an organic–inorganic hybrid strategy that overall improves the electrode-level specific energy at high rates for meeting practical metrics. This work demonstrates the potential of organic electrodes for high-power output under extreme operational conditions.
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